What technical writing tools should I learn?

I use ClickHelp, and you don't need to learn it because the UI is intuitive, and it's easy to use this technical writing tool. 

In technical writing various writing tools are used, few are named below:

1. MS Office - Word and Power Point

2. Adobe FrameMaker

3. Adobe Robohelp

4. ArborText Editor

5. oXygen

6. SnagIt

7. Camtasia Studio

8. Xmetal

9. SAP

10. Madcap flare